Determining the effectiveness of drought resilient bioretention bed in storm water management
Date
2022-03-17
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Abstract
Bioretention is a modern low-impact development (LID) technique that constitutes a vegetated depression filled with a permeable filtration medium, which can improve stormwater quality, reduce peak-flow runoff, and prevent groundwater drought in urbanized watersheds. This study investigates the performance of a full-scale bioretention system to capture, treat, and store retained stormwater runoff. A new feature of this bioretention system, treated retained water, is then used to irrigate four nearby vegetation beds. This bioretention system, and the use of treated retained water, is a novel drought resilience design for bioretention system. A full-scale bioretention system (88 m2) was constructed in the fall of 2019 near Meadow Ridge School, Okotoks, Alberta, and vegetation was planted during the spring/summer of 2020. Bioretention performance in capturing runoff and treating stormwater was monitored from winter 2019 to summer 2020. The drought resilience bioretention system retained approximately 30 m3 in its drainage layer and roughly 4 m3 in the media layer. The monitoring system inside the reservoir chambers showed that the bioretention bed captured over 90% of stormwater runoff in 10 out of 13 rain events, and the retained runoff was used for irrigation during the spring/summer of 2020. The stormwater runoff retention for the other 3 rain events ranged from 30% to 77% according to the water level monitoring system. Four nearby vegetation beds were irrigated approximately 1 cm depth/day from June 2020 until the end of July 2020. Further adjustments to the irrigation setup would allow the vegetation beds to be watered all year round without using potable water. The water that was captured during the spring/summer of 2020 was of better quality than the water captured during the winter of 2019; most of the water quality indicators’ concentration declined substantially and stabilized at low concentrations. In spring/summer 2020, average concentrations for each water quality indicators are: total nitrogen (TN): 2.38 mg/L; ammonia (NH3-N): 0.13 mg/L; nitrate (NO3—N): 1.39 mg/L; total phosphorus (TP): 0.37 mg/L; reactive phosphorus (PO4-P): 0.1 mg/L; chemical oxygen demand (COD): 484.15 mg/L; total suspended solid (TSS): 39.23 mg/L; volatile suspended solid (VSS): 20.56 mg/L. Although the drought resilience bioretention system did not treat stormwater as well as other techniques, especially in treating TP concentration, the system was only established for one season, and an extended research period is required because the media of the system need time to stabilize, and vegetation needs to extend its root network to obtain optimal bioretention system performance.
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Truong, P. T. H. (2022). Determining the effectiveness of drought resilient bioretention bed in storm water management (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.>